1. Field of the Disclosure
The present disclosure relates to a method for producing a complex of tris-orthometallated iridium that is suitably used as a material for an organic electroluminescence device, and particularly to a complex of tris-orthometallated iridium capable of increasing the production yield of a facial isomer of tris-orthometallated iridium which has high light emission efficiency and is excellent in thermal stability.
2. Discussion of the Background Art
Currently, organic electroluminescence devices receive attention as a next-generation display technique or lighting technique, and development of light emitting materials for organic electroluminescence devices are extensively conducted. Light emitting material can be classified into two types: fluorescence materials and phosphorescence materials, but attention is focused on phosphorescence materials which show higher light emission efficiency. Among them, complexes of tris-orthometallated iridium represented by tris(2-phenylpyridinato)iridium are a promising group of materials because they show high light emission efficiency and good thermal stability. So far, many production methods have been disclosed for obtaining such complexes of tris-orthometallated iridium (see, for example, Patent Documents 1 to 5).
Patent Document 1 discloses a method, wherein as shown in the reaction formula (chemical formula 1), a chlorine-bridged iridium dimer is synthesized from iridium trichloride n-hydrate, and used as a raw material to produce a complex of tris-orthometallated iridium.

Patent Document 2 discloses a method, wherein as shown in the reaction formula (chemical formula 2), a chlorine-bridged iridium dimer is synthesized from iridium trichloride n-hydrate, and an iridium complex coordinated with acetylacetone is synthesized from the chlorine-bridged iridium dimer, and used as a raw material to produce a complex of tris-orthometallated iridium.

Patent Document 3 discloses a method, wherein as shown in the reaction formula (chemical formula 3), a chlorine-bridged iridium dimer is synthesized from iridium trichloride n-hydrate, and an iridium complex coordinated with acetonitrile is synthesized from the chlorine-bridged iridium dimer, and used as a raw material to produce a complex of tris-orthometallated iridium.

The production methods described in Patent Documents 1 to 3 are methods in which a complex of orthometallated iridium such as a chlorine-bridged iridium dimer is mixed with a bidentate organic ligand such as 2-phenylpyridinato, and the mixture is thereafter reacted under heating.
Patent Document 4 discloses a method, wherein glycerol as a reaction solvent is heated at 130° C. to 140° C. for 2 hours, and thereafter cooled to 100° C., 1-phenylisoquinoline and Ir(acac)3 (acac: acetylacetone) are placed in the cooled glycerol, and the mixture is reacted under heating at around 210° C. for 7 hours to produce a complex of tris-orthometallated iridium. Patent Document 5 discloses a method, wherein a mixture of a bidentate organic ligand and glycerol is heated at 150° C. for about 60 minutes, and cooled, Ir(acac)3 is thereafter added, and the mixture is heated to 200° C. to produce a complex of tris-orthometallated iridium.